Method and apparatus for sidelink synchronization signal transmission and reception in communication system based on unlicensed band

Abstract

A method performed by a user equipment (UE) in a wireless communication system is provided. The method includes identifying whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or a licensed spectrum, identifying a period for a transmission of a sidelink synchronization signal block (S-SSB) and a subcarrier spacing associated with the S-SSB, identifying a number of S-SSB transmissions within the period, and in case that the frequency band corresponds to the unlicensed spectrum, transmitting at least two S-SSBs, wherein the number of S-SSB transmissions relates to the subcarrier spacing and depends on whether the frequency band corresponds to the unlicensed spectrum or the licensed spectrum, and wherein a number of S-SSB transmissions in a case of the frequency band corresponding to the unlicensed spectrum is greater than a number of S-SSB transmissions in a case of the frequency band corresponding to the licensed spectrum.

What is claimed is: 
     
       1. A method performed by a user equipment (UE) in a wireless communication system, the method comprising:
 identifying that a frequency band in which the UE operates corresponds to an unlicensed spectrum; 
 identifying a period for a transmission of a sidelink synchronization signal block (S-SSB) and a subcarrier spacing associated with the S-SSB; 
 identifying a number of S-SSB transmissions within the period, for the unlicensed spectrum; and 
 transmitting at least one S-SSB based on the number of S-SSB transmissions, in the unlicensed spectrum, 
 wherein the number of S-SSB transmissions relates to the subcarrier spacing, 
 wherein the number of S-SSB transmissions for the unlicensed spectrum is greater than a number of S-SSB transmissions for a licensed spectrum, and 
 wherein transmitting the at least one S-SSB includes:
 identifying whether a first channel access procedure for transmitting a S-SSB fails on a first resource among resources corresponding to the number of S-SSB transmissions for the unlicensed spectrum, 
 in case that the first channel access procedure is fails, performing a second channel access procedure on a second resource among the resources corresponding to the number of S-SSB transmissions, and 
 in case that the second channel access procedure succeeds, transmitting a S-SSB on the second resource. 
 
 
     
     
       2. The method of  claim 1 ,
 wherein the period is 160 ms, and 
 wherein in case that the subcarrier spacing is 15 kHz, the number of S-SSB transmissions is 2. 
 
     
     
       3. The method of  claim 1 , wherein the S-SSB includes a sidelink primary synchronization signal (S-PSS), a sidelink secondary synchronization signal (S-SSS), and a physical sidelink broadcast channel (PSBCH). 
     
     
       4. The method of  claim 3 , wherein in case that the frequency band corresponds to the unlicensed spectrum, the PSBCH includes information indicating a channel access type. 
     
     
       5. The method of  claim 1 , further comprising:
 transmitting a physical sidelink control channel (PSCCH) or a physical sidelink shared channel (PSSCH) in symbols other than symbols in which at least one S-SSB is transmitted in a slot. 
 
     
     
       6. The method of  claim 1 , wherein the at least one S-SSB is received from a base station or another UE operating in the unlicensed spectrum. 
     
     
       7. A user equipment (UE) in a wireless communication system, the UE comprising:
 a transceiver; and 
 a controller coupled with the transceiver and configured to:
 identify that a frequency band in which the UE operates corresponds to an unlicensed spectrum, 
 identify a period for a transmission of a sidelink synchronization signal block (S-SSB) and a subcarrier spacing associated with the S-SSB, 
 identify a number of S-SSB transmissions within the period, for the unlicensed spectrum, and 
 transmit at least one S-SSB based on the number of S-SSB transmissions, in the unlicensed spectrum, 
 
 wherein the number of S-SSB transmissions relates to the subcarrier spacing, 
 wherein the number of S-SSB transmissions for the unlicensed spectrum is greater than a number of S-SSB transmissions for a licensed spectrum, and 
 wherein, for transmitting the at least one S-SSB, the controller is configured to:
 identify whether a first channel access procedure for transmitting a S-SSB fails on a first resource among resources corresponding to the number of S-SSB transmissions for the unlicensed spectrum, 
 in case that the first channel access procedure is fails, perform a second channel access procedure on a second resource among the resources corresponding to the number of S-SSB transmissions, and 
 in case that the second channel access procedure succeeds, transmit a S-SSB on the second resource. 
 
 
     
     
       8. The UE of  claim 7 ,
 wherein the period is 160 ms, and 
 wherein in case that the subcarrier spacing is 15 kHz, the number of S-SSB transmissions is 2. 
 
     
     
       9. The UE of  claim 7 ,
 wherein the S-SSB includes a sidelink primary synchronization signal (S-PSS), a sidelink secondary synchronization signal (S-SSS), and a physical sidelink broadcast channel (PSBCH), and 
 wherein, in case that the frequency band corresponds to the unlicensed spectrum, the PSBCH includes information indicating a channel access type. 
 
     
     
       10. The UE of  claim 7 , wherein the controller is further configured to:
 transmit a physical sidelink control channel (PSCCH) or a physical sidelink shared channel (PSSCH) in symbols other than symbols in which at least one S-SSB is transmitted in a slot, 
 wherein the at least one S-SSB is received from a base station or another UE operating in the unlicensed spectrum.